1. Field of the Invention
This invention relates generally to semiconductor manufacturing and, more particularly, to total tool control for semiconductor manufacturing.
2. Description of the Related Art
A semiconductor fabrication facility typically includes numerous processing tools used to fabricate semiconductor devices. The processing tools may include photolithography steppers, etch tools, deposition tools, polishing tools, rapid thermal processing tools, ion implantation tools, and the like. Wafers (or wafer lots) are processed in the tools in a predetermined order and each processing tool modifies the wafers according to a particular product design and/or operating recipe so that a desired product is formed in or on the wafer. For example, a photolithography stepper may be used to form a patterned layer of photoresist above the wafer. Features in the patterned layer of photoresist correspond to a plurality of features, e.g. gate electrode structures, which will ultimately be formed above the surface of the wafer.
Operation of the processing tools in the semiconductor fabrication facility is generally monitored and/or controlled by a variety of control units, each of which is responsible for a different aspect of the fabrication process. For example, the semiconductor fabrication facility may include one or more electrical test monitors for monitoring results of electrical tests performed on completed products. The semiconductor fabrication facility may also include one or more statistical process control (SPC) units, run-to-run (RtR) controllers, fault detection and control (FDC) units, dynamic adaptive sampling controllers, and the like. The control units in the semiconductor fabrication facility operate largely independently of one another. For example, the statistical process control units may make decisions regarding operation of one or more processing or metrology tools based on statistical process control charts formed with information collected from the processing or metrology tools. However, the statistical process controllers may not account for data collected by, or actions taken by, other control units such as the run-to-run (RtR) controllers, the fault detection and control (FDC) units, and the dynamic adaptive sampling controllers.
Failing to account for data collected by, or actions taken by, other control units may reduce the ability of the semiconductor fabrication facility to detect potential problems associated with one or more of the processing tools. For example, the fault detection and control unit may detect faults in processed wafers using metrology data collected from the processed wafers, which may trigger a modification in some aspect of the processing performed by one or more of the processing tools. However, since the fault detection and control unit operates independently of the other control units, the other control units may not be able to take actions that may compensate for, or supplement, the efforts of the fault detection and control unit. In some cases, one or more of the control units may take actions that directly conflict with the actions taken by other control units. Consequently, the control units' ability to anticipate problems with one or more tools and/or take corrective actions when problems are detected, may be limited by the functional independence of the control units.
The independence of the various control units may also limit (or eliminate) the control units' ability to cross check decisions made by different control units. For example, one fault detection control unit may be less reliable than other fault detection control units in the semiconductor fabrication facility. However, it may not be possible to use the more reliable fault detection control units to verify decisions made by the less reliable fault detection control unit. Consequently, processing tools may be erroneously taken out of production, or erroneously allowed to continue production, by the less reliable fault detection control unit.
The present invention is directed to addressing the effects of one or more of the problems set forth above.